Protector for electric ceicuits



A. M. CURTIS.

PROTECTOR FOR ELECTRIC CIRCUITS.

APPLICATION FILED NOV. I. new.

1,325,889. Patented Dec. 23,1919.

# 9 kg c 7147065566. //7 venfori' W /M/K/ lAffJt" UNITED STATES PATENT OFFICE.

AUSTEN M. CURTIS, 0F BROOKLYN, NEW YORK, ASSIGNOB, BY MESNE ASSIGNMENTS, TO WEBTEBN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

PROTECTOR FOB ELECTRIC CIRCUITS.

flpecmoation of Letters Patent. Patented Dec, 23, 1919,

Application flied November 1, 1915. Serial 1T0. 69,056.

To all whom it may concern:

Be it known that I, AUBTEN MANSFIELD CUR'rIs, a citizen of the United States residin at Brooklyn, in the county of Kings and tate of New York, have invented certain new and useful Improvements in Protectors. for Electric Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to a protect' device for electric circuits. Its object is to protect an electric circuit against high impressed voltages by diverting a portion of the power supplied by the source of impressed voltage around the receivin circuit, the ratio of this diverted power to the power consumed in the said circuit being r the higher the im ressed volta T is object is accomplis ed by actuzfil y or effectively shuntin the electric circuit to be protected by an e ectrical conductor which has the property that its resistance decreases with increasing applied voltage. Under these circumstances, as the voltage impressed across the terminals of the electric circuit and the protecting device is increased, the ratio of current in the protecting conductor to that in the protected circuit Wlll increase.

Protection of this kind is particularly desirable in signalin systems, for example in wire or wireless to egraph or telephone systems in which the receiving device is often subjected to impulses of comparativel high voltage, the effect of which is to deafiin t e operator and consequently to render the signals following the disturbing impulse unintelligible.

The nature of this invention will be more fully explained in connection with the drawings, in which Figure 1 represents the simplest embodiment of this invention; Fig. 2 represents a slightly different form in whlch it is possible to send a continuous current through the protecting conductor- Fig. 3 shows a form in which it is possible to adjust the efi'ective resistan e of the rotecting conductor with respect to that o the receiving circuit to secure maximum effect. In all these figures corresponding parts are denoted by like reference numbers.

Referring to Fig. 1, 1 re resents a generator or other source of V0 tags which is to be impressed upon the receivini, device 2, which latter may be, for examp e, an ordinary telephone receiver. 3 is the protecting conductor and consists of a block of substance whose resistance decreases with increase of apfilied voltage, contact being made with t block by means of metallic plates. Connections from these metallic plates or electrodes serve to connect the device in shunt to the receiving instrument 2. It has been found that many materials, notably carborundum and the oxids or silicides of certam substances, possess this property. Some crystalline substances also behave in this manner. It will be obvious that if the resistance of the receiving device 2 remains constant with increasing impressed voltage, and if the resistance of the cell 3 decreases with increasing voltage, the result will be that for high voltages a ver much larger part of the total current delivered by the gfnerator will flow through the cell 3 than t rou h the receiving instrument 2. On the other and, for low voltages the cell 3 may be so constructed as to divert only a small fraction of the available power from the receiver.

Referrin to F i 2, a system is shown which is a. apted %or receiving alternating currents from the generator 1. It is also so arranged that continuous current may, if desired, be super osed upon the alternating current flowing t rough cell 3. It has been found that in some cases this superposition of continuous current improves the operation of the device. In this figure, 4 is a transformer by means of which the receiving apparatus is connected to the line, (3 is a battery which supplies the continuous current just mentioned, and 5 is. a condenser which may be inserted if desired to prevent the flow of continuous current in the receiving apparatus 2.

Referrlng to Fig. 3, an arrangement is shown in which the protecting cell may be supplied with continuous current as before, and in which also the effective resistance shunting the receiving device may be adjusted to any desired value. In this figure the protecting cell is not shunted directly across the receivin instrument but is connected in circuit with thesecondary of the transformer 4 whose primary shunts the receiver 2. Since it is well known that the apparent resistance introduced into the prunary of a transformer, due to a reslstance in its secondary, is found from the secondary resistance by multiplying it by the square of the ratio of turns on the former, it will be seen that the effective shuntin resistance maiy be made-to have any desired value by a justing the new!" the battery 6 may be omitted if the use of a larizing direct current is not required. it will be obvious that many other methods may be used for effectively inserting such a protecting cell in shunt with a receiving device without departing. from the spirit of this invention.

What is claimed is:

1. The combination of a line, a telephone receiver therefor, at protecting devicev for said receiver, said device comprising a resistance which decreases with increasing applied voltages, and means for supplying a polarizing potential to said device.

2. The combination of means to be protected from excessive voltages, a protective device thcrefor, comprising resistance which decreases with increasing applied voltages, a source of current for said means, and means for polarizing said device.

3. The combination of means. to be protected from excessive voltages, a protective device in shunt thereto, coinprisin resistance which decreases with increasing applied voltages, a source of current for said means, and means for polarizing said de vice.

l. The combination of a line, means for supplying to said line impulses to be transmitted, a protective device for said line comprising carborundum, and apelarizing source of current for said carborundum.

5. A protective system comprising a telephone receiver, a protective device comprising a carborunduin by-path for said rece1ver,' means comprising a source-of voltage for supplyin current to said carborundum, and means or preventing flow of current from said source to said receiver.

6. A protective system comprising a line subject to an electrical disturbance, means to be protected associated with said line, and a protective device .comprisin resistance which decreases with increasing applied voltages, said device "being inductively coupled to saidline.

7. A protective system comprising a line, a telephone receiver therefor, a protective -device comprising. carborundum in shunt to said receiver and inductively coupled to said line, and asource of current for polarizing said earborundum.

8. A protective system comprising a line, a telephone receiver therefor, and carborun- .dum connected in shunt to the sides of said plied volt es, a source of current for said means, an means for polarizing said resistanee.

11. A protective system comprising a line, a telephone receiver therefor, a rotcctive device comprising carborundum in circuit with said receiver and inductively coupled to said line, and a source of current for polarizing Said carborundum.

l2. Aprotective system comprising a line,- a telephone receiver therefor, and a low impedance by-path comprising carborundum in circuit with said receiver.

18. A signaling system oomprisin a line, atelephone receiver therefor, and a negative resistance by-path connected in shunt to said-receiver for preventing a tone of supernormal intensity in said receiver.

In witness whereof, I hereunto subscribe my name this fourth day of October A. D.,

AUSTEN M. CURTIS.

It is hereby certified that in Letters Patent No. 1,325,889, granted December 23,

1919, upon the application of Austen M. Curtis, of Brooklyn, New York, for an improvement in Protectors for Electric Circuits, errors appear in the printed specification requiring correction as follows: Page 2, claims 8, 9, and 12, lines 59,

63, and 80, for the word protective read telephone; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 14th day of December, A. D., 1920.

[SEAL] L. B. MANN,

Acting Commissioner of Patents. Cl. 175-30.. 

